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Technical requirements for expansion joint plates 1. Requirements for tube bundles 1.1 The tubes and the tube plate shall be joined by strength expansion joining, and the outer diameter deviation of the tubes should be controlled within ±0.1mm； The hardness value of the heat exchange tubes should be lower than that of the tube sheet ； 1.2 Before the pipe passes through the holes in the tube sheet, its ends and outer surface should be polished to remove rust and reveal a metallic shine; there should be no burrs, wrinkles, scratches, metal shavings, oil stains, or oxide scale ； The grinding length should be 50-100 mm longer than the double tube sheet connection dimension ； 1.3 The polished tubes should be inspected for the ellipticity of their ends, outer diameter, and wall thickness, with records to be kept; tubes that exceed the allowable dimensional tolerances must be rounded before they can be used ； 1.4 The tubes should be able to pass freely through the holes in the tube sheet; forced insertion is not allowed ； 2. Requirements for tube sheets 2.1 Tube sheets shall be processed using a drilling and reaming method; fixed fixtures for the drill bits and reamers should be used during processing to prevent the hole dimensions from exceeding the specified limits due to bending or deformation. 2.2 The inner wall roughness Ra value of the tube sheet holes shall not exceed 12.5 μm ； The surface of the tube holes in the tube sheet must be cleaned thoroughly; there should be no burrs, shavings, rust spots, oil stains, or any other elements that could affect the quality of the expansion jointing or welding ； The surface of the expansion joint hole shall be free from defects such as longitudinal or spiral scratches that could affect the quality of the expansion joint. 2.3 The perpendicularity of the tube sheet holes shall meet the tolerance class 9 of GB1184 \"Tolerances for shape and position\". 3. Expansion joint requirements 3.1 For strength expansion joints, an expansion process test should be conducted prior to expansion: to determine the appropriate expansion degree ； and adopts a expansion joining process of adhesive expansion plus strength expansion ； 3.2 The expansion joint shall not extend beyond the back side of the tube sheet (the shell side). There shall be a smooth transition between the expanded and unexpanded sections of the heat exchange tubes, with no sharp edges. 3.3 When the expansion-first then welding process is used, lubricants that may affect welding quality shall not be employed. 3.4 For heat exchange tubes that tend to undergo cold work hardening and require resistance to stress corrosion, a flexible expansion jointing method is recommended. 3.5 Before expansion jointing, it should be checked that the tube sheet holes are free of defects such as sharp corners, burrs, and scratches ； 3.6 Use an inner diameter micrometer to measure the diameter deviation, ovality, and cylindricity of the hole; record these values and compare them with the measurement data of the tube’s outer diameter and wall thickness, in order to prepare the necessary data for expansion jointing ； 3.7 During the expansion fitting operation, it should be checked that the surface of the expansion tool is free from dust, metal shavings, rust, and similar contaminants ； 3.8 After expansion joint installation, an endoscope inspection shall be carried out; the expansion joint surface must be free of defects such as folds and cracks ；